Recent research has conceptualized sustainability as the environmental efficiency of wellbeing (EWEB). This concept takes into account the benefits societies are able to produce from their demands on the environment. Research along these lines indicates that countries vary widely in the efficiency with which they transform the Earth’s resources into well-being. Here, we take up this finding as a puzzle to be explained. We construct a new measure of EWEB using the ecological footprint per capita (a measure of environmental consumption) and average life satisfaction (a measure of subjective well-being). We draw hypotheses from political economy, modernization, and sustainable consumption theories in the environmental social sciences. Using full information maximum likelihood estimation, we test the effects of climate, political, economic, and social factors on EWEB with a sample of 105 countries. Key findings include a negative quadratic effect of economic development on EWEB, a negative effect of income inequality, and a positive effect of social capital.